Results of the National Lung Screening Trial (NLST) are in!

Enrollment was 8/2002 to 4/2004. Follow-up was through end of 2009. Patients were age 55-74, with >30 pack-year smoking history, still smoking or quit <15 years. Intervention / Control: Low-dose chest CT vs. chest plain films thrice-yearly.

By screening these 53,454 high-risk people, 62 deaths per 100,000 person-years were prevented (247 vs. 309; relative risk reduction of 20%). A full 39% of those screened had at least one positive/abnormal CT scan. One-quarter of all CT scans were abnormal, and 96% of those were false-positives. The number needed to screen with CT to prevent one lung cancer death was 320. (n=53,454)

Complications from invasive diagnostic evaluation:

About 1.5% of participants were affected overall (but out of 53,454 that's more than 8,000 people). For those who ultimately did not have cancer, abnormal scans led to a major complication from an invasive procedure only 0.06% of the time. (But 11% of the scans ultimately found to show cancer were associated with a major complication.) Twenty-six people died within 60 days after an invasive procedure (causality unclear); 20 of the 26 had lung cancer.

Some overdiagnosisis strongly believed to have occurred in the NLST, although overdiagnosis (by definition) cannot falsely account for the mortality benefit observed. An estimated 10-15 years must pass before the extent of stage-shift (overdiagnosis through detection of early stage cancers that would never invade or become lethal) that occurred in NLST can be determined.